Add comprehensive integration test suite and CI workflow for gh-models CLI

[Copilot]

This PR adds a comprehensive integration test suite that validates the gh-models CLI executable against live LLM endpoints using process execution rather than mocks, plus automated CI integration.

Problem

The existing test suite only included unit tests with mocked clients, which didn't validate:

• The actual compiled binary behavior
• Real process execution and exit codes
• File modification scenarios (e.g., prompt file augmentation)
• Live endpoint integration when authenticated
• End-to-end command workflows

Solution

Created a new integration test suite in integration/ that:

🏗️ Architecture

• Uses //go:build integration build tags to exclude from regular test runs
• Executes the actual compiled ./gh-models binary via os/exec
• Provides dedicated make integration-test command with proper build dependency
• Integration testing documentation moved to CONTRIBUTING.md for better discoverability

🧪 Test Coverage

Basic Commands (integration_test.go):

• Help functionality and usage information
• Error handling for unauthenticated scenarios
• Command argument validation
• Exit code verification

File Operations (file_modification_test.go):

• Prompt file parsing and validation
• File modification tracking for generate command
• Template variable handling
• Output format validation (JSON/default)
• File system interaction (permissions, working directory independence)

Authentication Scenarios (authenticated_test.go):

• Graceful handling of unauthenticated scenarios
• Ready for live endpoint testing when gh auth login is configured
• Error message validation and user guidance

🚀 CI Integration

GitHub Actions Workflow (.github/workflows/integration.yml):

• Runs automatically on pushes to main branch
• Includes required models: read permission for GitHub Models API
• Uses make integration-test to build binary and run integration tests
• Follows existing workflow patterns with proper concurrency handling

🎯 Key Features

# Integration tests are excluded from regular runs
make test        # Runs unit tests only (no integration package)

# Dedicated command for integration testing with build dependency
make integration-test   # Automatically builds binary + runs integration tests

# Exit code validation
./gh-models --help      # Exit code 0 (success)
./gh-models list        # Exit code 1 (auth required)

File Modification Validation:

// Track file changes for generate command
originalSize := getFileSize(promptFile)
runCommand("generate", promptFile)
newSize := getFileSize(promptFile)
// Validate file was augmented with test data

Live Endpoint Ready:

• Tests detect authentication status automatically
• Skip live tests when unauthenticated (CI-friendly)
• Full validation when gh auth login is configured
• Monitor actual API responses and file modifications

🔒 Safety & CI Integration

• Build tag isolation prevents accidental execution
• Graceful skipping when authentication unavailable
• No impact on existing development workflows
• Comprehensive error handling and logging
• Automated CI execution on main branch pushes

The integration test suite provides confidence that the CLI binary works correctly in real-world scenarios while maintaining the fast feedback loop of existing unit tests, with automated validation on every main branch update.

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[pelikhan]

@copilot rebase to main

[pelikhan]

add dependency on build step

[Copilot]

Added build as a proper dependency to the integration-test target. The target now correctly depends on build rather than calling it explicitly. (0d67cc7)

[pelikhan]

Move this section to contributing.md

[Copilot]

Moved the integration testing documentation from integration/README.md to CONTRIBUTING.md. The integration/README.md now contains just a brief description with a reference to the full documentation. (0d67cc7)

[Copilot]

@copilot rebase to main

I'm unable to perform a rebase operation due to system limitations that prevent force push operations. The changes in this PR can be rebased manually if needed, or the changes can be merged as-is to preserve the commit history.

[pelikhan]

@copilot Add GitHub action workflow step that builds and runs the integration tests only. Runs on pushes to main. Make sure to set the models: read permission

[Copilot]

@copilot Add GitHub action workflow step that builds and runs the integration tests only. Runs on pushes to main. Make sure to set the models: read permission

Added GitHub Actions integration test workflow in .github/workflows/integration.yml. The workflow runs on pushes to main, includes the required models: read permission, and uses make integration-test to build and run the integration tests. (969b0a2)

[pelikhan]

@copilot rebase branch

[Copilot]

@copilot rebase branch

I'm unable to perform a rebase operation due to system limitations that prevent force push operations. The branch contains the integration test suite commits (59e0381, 0d67cc7, 969b0a2) on top of the current main branch. If you'd like to rebase, this would need to be done manually using standard git rebase commands.